Flip-chip ball grid array (FCBGA) semiconductor package, as understandable from its name, uses a flip-chip technique to form electrical connection between a chip and a chip carrier (such as a substrate) that are incorporated in the semiconductor package. Particularly, a plurality of solder bumps are implanted on an active surface (i.e. a surface where electronic components are disposed) of the chip, and are bonded to the substrate so as to electrically connect the chip to the substrate.
As to heat dissipation of the FCBGA semiconductor package, there are two methods conventionally available as those disclosed in U.S. Pat. Nos. 5,311,402, 5,637,920, and 6,011,304. One method involves having the active surface of the flip chip mounted on the substrate by the solder bumps and having an inactive surface of the chip exposed from an encapsulant that encapsulates the chip, such that heat generated during the operation of the chip can be dissipated through the exposed inactive surface of the chip. The other method involves mounting a heat spreader on the substrate, wherein the heat spreader includes a flat portion, and a supporting portion connected to the flat portion and supporting the flat portion above the substrate. The flat portion of the heat spreader comes into contact with the flip chip, and is at least partly exposed from the encapsulant to dissipate the heat from the chip.
However, by the above methods, heat can only be dissipated through the exposed inactive surface of the chip or the exposed flat portion of the heat spreader, which usually does not provide satisfactory heat dissipating efficiency for the semiconductor package. Moreover, for the case having the flat portion of the heat spreader exposed, during a molding process for forming the encapsulant, which is performed after the chip and the heat spreader are mounted to the substrate, the heat spreader must have its top surface abutting against a top wall of a mold cavity used for shaping the encapsulant, so as to prevent resin flashes from being formed on the top surface of the heat spreader. This thus makes the fabrication processes of the semiconductor package become complicated.
Accordingly, U.S. Pat. Nos. 6,444,498 and 6,458,626 propose a flip-chip semiconductor package with a heat dissipating structure including a heat spreader mounted on a chip. The heat dissipating structure and the chip are integrally encapsulated by an encapsulant, with the heat spreader being completely exposed from the encapsulant. Such arrangement reinforces the whole structure of the semiconductor package and desirably improves the heat dissipating performance for the semiconductor package.
The above technology disclosed in U.S. Pat. Nos. 6,444,498, and 6,458,626 is however not considered suitable and feasible for use with a chip producing a very large amount of heat during operation, such as central processing unit (CPU). In other words, for such highly heat-generating chip, a mechanism that can even more improve the heat dissipating efficiency of the semiconductor package is required. To this end, U.S. Pat. No. 5,880,524 proposes a semiconductor package integrated with a heat pipe lid therein. As shown in FIG. 1, this semiconductor package 1 comprises a substrate 11, a flip chip 10 mounted on the substrate 11, and a lid 12 mounted on the substrate 11 and the chip 10. The lid 12 includes a first accommodating room 121 for receiving the chip 10 therein, and a second accommodating room 122 provided on the first accommodating room 121 and for accommodating a heat pipe 120 filled with a cooling fluid. A heat transfer layer 14 is disposed between a top surface 1211 of the first accommodating room 121 and the chip 10, such that heat produced from the chip 10 can be transmitted to the heat transfer layer 14 and then to the cooling fluid in the heat pipe 120. A heat sink 13 is mounted on the lid 12, and absorbs the heat of the cooling fluid in the heat pipe 120 and dissipates the heat out of the semiconductor package 1.
Although the foregoing heat pipe lid achieves better heat dissipating performance than the conventional heat spreader, it is adhered to the substrate and the chip and thus is liable to become detached therefrom, thereby leading to a reliability problem. Further, the contact area between the heat pipe lid and the chip is provided as the only heat dissipating area for the semiconductor package, which is not sufficient for accomplishing satisfactory heat dissipation performance.
U.S. Pat. No. 6,525,420 also discloses a semiconductor package integrated with a heat pipe and thus encounters the same drawbacks as above.
Therefore, the problem to be solved here is to provide a semiconductor package with heat dissipation for a chip therein being satisfactorily performed.